The battle for Debaltseve is over. On February 18, Petro Poroshenko, the Ukrainian president, ordered his troops to withdraw from the city in the Donetsk region in eastern Ukraine.

The soldiers hadn’t a chance of winning. They were easily outnumbered by pro-Russian forces, whom Moscow has supported throughout the conflict. As the Ukrainian soldiers made their way out of the bombed city, the ceasefire accord reached in Minsk on February 12 was in tatters.

Repeated calls by Angela Merkel, the German chancellor, to Vladimir Putin, the Russian president, to implement the ceasefire have gone nowhere. Diplomacy has failed. What is more, Europeans have not grasped the implications of Ukraine losing its territorial integrity.

European leaders can wring their hands. They can threaten to ratchet up the sanctions they have imposed against Russia. But the damage has been done ever since March 2014, when Putin annexed Crimea. Through its weak response to Russian aggression, the E.U. has discarded the rules of the post–Cold War era.

Even the 1975 Helsinki Final Act, in which Western and Communist bloc leaders pledged to respect the inviolability of borders, has been torn up. Europe is entering a new and dangerous era for which it is completely unprepared.

When it comes to facing real threats on their Eastern borders—meaning from Russia—European leaders still cling to the idea of soft power. Yet at the same time, several governments have joined the U.S.-led coalition to fight the terrorist threat coming from the Islamic State in Iraq and Syria.

Ursula von der Leyen, the German defense minister, who is overseeing a new white paper that refers to Russia as a threat, tried to explain the difference in approach between Russian aggression and jihadism. Speaking at the February 6–8 Munich Security Conference, von der Leyen said diplomacy could not work with the Islamic State because there was no one with whom to negotiate. Therefore, force was a viable option. That, she said, was not the case with Russia: there, the West had a negotiating partner.

Not any more, it seems. The failure of the latest ceasefire agreement in eastern Ukraine shows the futility of talking to the Russian president.

Some European leaders would beg to differ. The fulsome ways in which some leaders deal with Putin are shameful. They make a mockery of European unity and the appalling suffering of civilians in eastern Ukraine.

Viktor Orbán, the prime minister of Hungary, who feted Putin on February 18, is willing to make his country even more dependent on Russian energy by agreeing to Russian loans to build a new nuclear reactor near the central Hungarian town of Paks. That dependence carries a high price in the form of political interference. So far, Orbán has backed E.U. sanctions against Russia and NATO’s new reassurance role in Eastern and Central Europe. But that continuing support cannot be taken for granted.

Other European leaders, who seem to forget that a war is being waged on the E.U.’s borders, have no qualms either in dealing with Putin. Nicos Anastasiades, the president of Cyprus, is scheduled to visit Moscow on February 25. For many years, Cyprus has been providing Russian oligarchs with a safe haven for their riches.

Alexis Tsipras, the newly elected prime minister of Greece, has nonchalantly implied that he could turn to Russia for financial assistance if his talks with E.U. finance ministers over amending the terms of Greece’s bailout program fail. And don’t forget Miloš Zeman, the president of the Czech Republic, who is known for his pro-Russian stance. With leaders like these, it’s a wonder that the E.U. ever managed to push through its sanctions.

But there is a wider issue at stake: the Europeans’ unwillingness to defend Ukraine’s territorial integrity has set a precedent. Some would say that Russia tested the E.U.’s resolve in 2008 after its short invasion of Georgia. Then, the response by the E.U. and by the West in general was weak.

And as Russia over the past year began chiseling away at parts of eastern Ukraine, in November 2014 the Kremlin signed a security pact with the self-declared republic of Abkhazia, which Russia prized away from Georgia during the 2008 war.

With the fall of Debaltseve, Poroshenko had no option but to call on the United Nations and the E.U. to send peacekeepers to eastern Ukraine. Whatever the response to that request, the record of peacekeepers is to consolidate facts on the ground, not to undo them. That could suit Putin.

Poroshenko’s call also confirms how the E.U. and the United States failed to give the Organization for Security and Cooperation in Europe (OSCE) sufficient personnel and support to monitor either the September 2014 Minsk Protocol or the February 2015 ceasefire agreement. Pro-Russian separatists have done everything possible to hinder the OSCE monitors.

That aside, Europeans’ unwillingness to defend Ukraine’s territorial integrity is due to more than the reluctance of most E.U. governments to provide Ukraine with weapons. Apart from the endless arguments over whether sending arms would encourage Putin to escalate or de-escalate the war, this unwillingness also stems from the fact that most European governments do not believe Ukraine’s territorial integrity matters that much to their own security.

For most Europeans, the war in Ukraine—unlike the Islamic State—does not pose a threat to their way of life and their values. Yet the war has already called into question Europe’s values and the principle of inviolable borders. What European leader would deny that?